(a) Field of the Invention
The invention relates to a measurement circuit, particularly to an element measurement circuit built in a chip to measure characteristics of the chip.
(b) Description of the Related Art
When CMOS (complementary metal oxide semiconductor) process is developed into nanometer order, the influence of process variation on product becomes greater and thus increasing product yield is more difficult. To figure this problem, a test key is placed in each wafer to collect process information, and a measurement equipment or test machine is required to measure signal parameters. However, measuring signal parameters requires a high-end measurement equipment so that it introduces production cost and adding the equipments may further introduce an error. Furthermore, the test keys is limited in a wafer and is not sufficient to realistically reflect the process variation impacted in each die of the wafer. Therefore, in order to obtain related information to increase diagnostic or debugging capability to reduce production cost, it is necessary to build a circuit in a chip to measure characteristic of elements of the chip.